The present invention relates to a compound which is useful in silica-filled rubber compositions and the processing of a sulfur curable rubber composition containing silica.
Sulfur containing organosilicon compounds are useful as reactive coupling agents between rubber and silica fillers providing for improved physical properties. They are also useful as adhesion primers for glass, metals and other substrates.
U.S. Pat. Nos. 3,842,111, 3,873,489 and 3,978,103 disclose the preparation of various sulfur containing organosilicon compounds. These organosilicon compounds are prepared by reacting
(a) 2 moles of a compound of the formula
Zxe2x80x94Alkxe2x80x94hal
where hal is a chlorine, bromine or iodine; Z is 
where R1 is an alkyl of 1 to 4 carbon atoms or phenyl and R2 is alkoxy of 1 to 8 carbon atoms; or cycloalkoxy of 5 to 8 carbon atoms; or alkylmercapto with 1 to 8 carbon atoms; Alk is a divalent aliphatic hydrocarbon or unsaturated hydrocarbon or a cyclic hydrocarbon containing 1 to 18 carbon atoms; with
(b) 1 mole of a compound of the formula
xe2x80x83Me2Sn
where Me is ammonium or a metal atom and n is a whole number from 2 to 6.
Japanese Patent Application No. 124400-1984 and U.S. Pat. No. 4,820,751 each disclose a rubber composition containing a silicate-based filler and a compound containing siloxy groups and a benzothiazole group. One example of such compound is trimethyoxysilylpropyl-mercaptobenzothiazole-tetrasulfide.
The present invention relates to asymmetrical siloxy compounds of the formula: 
wherein R1, R2 and R3 are independently selected from the group consisting of alkoxy radicals having from 1 to 8 carbon atoms; R4 is selected from the group consisting of alkylene groups having from 1 to 15 carbon atoms and arylene and alkyl-substituted arylene groups having from 6 to 10 carbon atoms; n is an integer of from 2 to 8 and X is selected from the group consisting of 
and R5 is selected from the group consisting of alkyl groups having from 1 to 15 carbon atoms, aryl and alkyl substituted aryl groups having 6 to 20 carbon atoms.